You know, looking at this here mane and tail makes me remember Warhammer 40k's Warp Storms, particularly the Eye of Terror. Fitting, considering that this here is Nightmare Moon. The armour also makes me think Chaos. She is best Horus.

This looks like that castle on the moon from the comics, complete with nightmare forces and beasts. And the "hair hole" looks like it leads to Equestria.Dat border of the hair, by theway. And dem doubled rear hooves. Is it a mistake or an intentional distortion? Because if the second, then it's awesome and quite ingenious. Love the sheer detail of the armour with all the properly villainous fang-like spikes and sharp curves and points, as well as the colouration. Also, the cape makes it even more awesome. And dat horn spiral. Oh, and great lighting, to boot.Wonderful job!